Many beliefs of great practical import face difficulties spreading in the general population—beliefs in the efficacy of vaccination, in the dangers caused by global warming, in the safety of GMOs, and so forth. It can be argued that the primary obstacle these beliefs face is that they violate some of our intuitions—that injecting something drawn from someone sick into someone healthy is a bad idea, for instance. However, there are cognitive mechanisms designed to overcome any negative initial reaction one might have towards counter-intuitive beliefs—in particular, mechanisms of trust and argumentation. It has been suggested that these mechanisms work rather poorly: that people are either not deferential enough, or are too deferential, that they accept too many or too few arguments. I will argue on the contrary that these mechanisms work, on the whole, very well, and can make people accept counter-intuitive beliefs. I will point to another obstacle in the spread of counter-intuitive beliefs: the difficulties faced by people who have accepted these beliefs to convince others in turn. I will present a series of experiments showing that people who have accepted a counter-intuitive belief on the basis of trust or argumentation can find it difficult to produce arguments that would convince someone else to accept this belief. These difficulties should hinder the spread of counter-intuitive beliefs in the general population.